1. Technical Field
The present invention relates to a key and more particularly to a capacitive sensitive key structure which uses capacitive sensing of electrostatic changes and provides a sense of touch feedback.
2. Description of Related Art
Conventional keys are mostly mechanical and each comprises a cap, a key portion and a circuit board. The circuit board is disposed beneath the key portion. The cap fits around the key portion. The key portion has therein a resilient component and a sensing component. A metal layer is disposed on the circuit board and corresponds in position to the key portion. The resilient component deforms as soon as the key portion is pressed, so as to move the key portion downward and drive the sensing component to come into direct contact with the metal layer on the circuit board, thereby enabling the key portion to electrically connect with the circuit board and turn on. The circuit board generates an electrical signal in accordance with the circuit driven by the key portion to thereby turn on or control a tool or an electronic product, wherein the displacement of the key portion provides a sense of touch feedback to the pressing finger. However, the key portion of the conventional mechanical key and the surface of the circuit board or keyboard casing are separated by a gap. As a result, external moisture is likely to intrude into the key portion and the circuit board through the gap. For this reason, the metal layer on the circuit board is likely to be oxidized and damaged, thereby compromising or even precluding the electrical contact between the key portion and a contact terminal. Furthermore, the cap of the conventional mechanical key is made of a rigid material and thus is so brittle as to be susceptible to damage. However, due to the advancement of touch technology, touchscreens also function as touch keyboards. The touch surface of a conventional touch keyboard usually functions as the surface of a flat panel. External moisture is prevented from intruding into the panel, and electrical signal transmission begins with a touch given to the panel; however, touch keys nowadays cannot provide a segmental sense of touch feedback to the key portion of a key. As a result, it is impossible to determine whether the required key is correctly touched. Furthermore, since the key portions of the keys are not physically separated, the odds are that neighboring keys are wrongly touched to therefore cause erroneous control. Although it is feasible that the key of the touch panel may have a vibration component to provide after-touch vibration feedback, the vibration component adds to the manufacturing costs greatly, nor does it provide a solution to overcome the aforesaid drawbacks of the prior art, that is, failure to determine whether the required key is correctly touched, and a wrong touch arising from a lack of physical separation.